Image-yielding elements and processes



States Patent Offiw 3,529,963 Patented Sept. 22, 1970 U.S. Cl. 96-50 8 Claims ABSTRACT OF THE DISCLOSURE Image-yielding elements comprising (a) a silver salt of a highly fluorinated alkanesulfonic acid or dodecahydrododecaboric acid, said acids having a pKa no greater than 2, (b) a photosensitizer which may be a photoreducible dye capable under actinic radiation of decomposing said salt to liberate the acid, (c) a hydrogen abstractable material, and (d) a polymer binder, and optionally (e) an acid-sensitive material preferably an aldehyde precursor and/or (f) water or a water-yielding material; and processes of image formation by exposing the elements to actinic radiation and heating them to form an image.

This application is a continuation-in-part of my prior application Ser. No. 468,977 filed July 1, 1965 and entitled Image-Yielding Elements and Processes (now abandoned).

This invention relates to new photographic image-forming elements and to a new process of image formation.

The conventional photographic process has been Widely used to produce copies of original matter. This process has yielded high quality reproductions but has been time consuming and expensive since various steps of photographic processing are involved, e.g., exposing, developing, fixing, Washing and drying. More rapid processes of image reproduction have been developed such as thermography, electrostatic image reproduction, etc. but these processes are more suited for copying simple images such as a printed text or a line drawing. These latter processes are not generally capable of making copies which even approach the high quality of those copies made by the conventional, wet photographic process. Furthermore, the rapid, dry processes often require elaborate and expensive equipment and the light sensitivity of the elements employed in such processes is relatively low.

An object of this invention is to provide a process capable of forming high quality images by simple, rapid and dry processing and requiring only simple and inexpensive equipment. A more specific object is to provide a process which can produce images having very high transmission optical densities on a fog free background. A further object includes the formation of high resolution, very fine grain images from relatively high speed photographic elements. A still further object is to provide simple and dependable elements for use in the process. Still further objects will be apparent from the following description of the invention.

The novel image-yielding elements of this invention have an image-forming layer comprising:

(a) A silver salt of a perfluoroalkanesulfonic or betahydroperfiuoroalkanesulfonic acid,

(b) A photosensitizer capable, upon absorption of actinic radiation, of decomposing said silver salt to liberate a strong acid,

(c) A hydrogen abstractable material or compound which is a hydrogen donor for said photosensitizer during its absorption of actinic radiation,

(d) A carrier, preferably a film forming organic polymer binder free from substantial amounts of labile covalent halogen, and optionally (e) An acid-sensitive organic material which produces a color change in the presence of a strong acid (i.e., an acid having a pKa no greater than 2.0), said color change being suificient to form a visible image, and/ or (f') Water or a water-yielding material or compound.

Preferably, the organic material (e) contains :a plurality of units of the structure wherein X is 0 011, -OR, 0( i0-R or halogen, wherein R is alkyl or aryl, and wherein HX is readily removable from the unit in exposed areas to cause the above change in color suflficient to form a visible image.

Component (b) may be a photoreducible ketone, e.g., a quinone, an alph-a-diketone; or a photocleavable compound such as benzpinacolone, a polychlorinated biphenyl or bromonaphthalene which, upon irradiation, liberates a strong acid.

The photosensitizer may also be a photoreducible dye in the presence of a mild reducing agent which has a reduction potential less than that necessary to reduce the dye or metal salt in the absence of actinic radiation. Suitable photoreducible dyes are disclosed in Oster, U.S. 2,875,047 (Feb. 24, 1959).

Component (e), the acidsensitive material, is preferably an aldehyde precursor hydrolyzable to an aldehyde by a strong acid. In the particularly preferred embodiment, component (e) is a polymeric acetal which contains intralinear units of the structure CH2CH-CH2CH O 0 c R where R is H or CH CH CH and which can also function as a hydrogen abstractable compound (c), as a water-yielding material (f), and a binder (d). When component (e) is polymeric it should form strong coherent films and act as a binder. The polymeric acetal may either have the acetal groups present as pendent groups on a polymeric backbone or may contain the acetal groups as part of a linear polymer chain.

The hydrogen abstractable compound (c) can, as disclosed above, be supplied by the organic polymer binder (d). Component (c) can also be a separate component such as an alcohol, or acetal. Component (c) which can also be designated as a hydrogen donor compound may be diethylene glycol and its monomethyl ether or diacetic acid ester, a polyethylene glycol of molecular weight 400- 6000, or tetraethyl malondialdehyde acetal.

With regard to component (d), the polymeric binder should be free from labile, covalent halogen and preferably free from basic groups. Suitable classes and specific binders are listed in Burg et al. U.S.P. 3,060,023. Nonthermoplastic binders can be made thermoplastic by addition of a suitable plasticizer, e.g., dibutyl phthalate, tricresyl phosphate, etc. In some instances a single compound may serve two or more functions as listed above.

Component (f) when not water can be a hydrated material such as pinacol hydrate. Water can be produced by the acid catalyzed dehydration of hydroxy compounds such as pinacol or from a material serving some other function, e.g., from a polyvinyl acetal (e) if it is not completely acetalized.

The process of this invention comprises 1) exposing, imagewise, to actinic radiation (preferably radiation predominating in wavelengths in the ultraviolet and visible regions of the spectrum) an image-yielding element having an image-forming layer containing components (a), (b), (c), (d) and, if desired, components (e) and (f), that are described above, to form a colored image in said stratum; and

(2) uniformly heating the exposed stratum to a temperature between 60 and 200 C., preferably from 100 to 170 C. to effect the dry development of a metalcontaining image. The heating time may vary from a few seconds to five minutes or more with shorter exposure times requiring higher temperatures and vice versa. Also, as the amount of exposure in step (1) is increased, the time and/or temperature of the heating may be reduced. Steps (1) and (2) may be combined in a single step if the source of radiation also produces appreciable heat, e.g., a carbon arc. Optionally there is added a step (3) of fixing or stabilizing the' developed image, e.g., by (a) complete wash-out of the unexposed image areas or (b) thermal transfer of the unexposed image areas to a separate, receptive support, followed by re-exposure and/or reheating of the transferred image. Still other methods of stabilizing the image can be employed, e.g., partial washout by using a solvent system that removes the metallic salt (a) and/or the photosensitizer (b) or by dusting or stripping techniques disclosed in U.S.P. 3,060,024 and 3,060,025.

In stabilizing the image by such processes as washout or thermal transfer, the process can be controlled to yield either a positive or a negative image by selection of the binder. For example, a polymeric acetal in which the acetal groups are pendent on a polymeric backbone can be imagewise cross-linked so that the unexposed areas are removable by washout or by thermal transfer. On the other hand, a linear polymeric acetal can be imagewise depolymerized to become removable in the exposed areas by washout or thermal transfer.

The invention will be further illustrated but is not intended to be limited to the following examples.

EXAMPLE I A photosensitive binder solution was prepared as follows:

Polyvinyl formal 1 (15% by wt. sOln. in 40 ethanol/ 60 toluene by wt.)15.0 g.

9,10-phenanthrenequinone-0.l3 g.

Dioxane-4.0 ml.

The solution was coated on various film bases including polyethylene terephthalate (the resin subbed base described in Example IV of U.S.P. 2,779,684), paper, and aluminum and allowed to air dry. The photosensitive layer was exposed for 5 seconds at a distance of 12 inches through a letter text photographic negative to the radiation of a high-intensity photolight (Sylvania Sun Gun Model SG 60, Lamp Type DXN). Later heating the layer to 150 C., in less than 1 minute effected the dry development of a black image. In a similar manner a copy was obtained using a halftone photographic negative. By exposing through a 21-step continuous tone photographic step tablet having an approximate density range of 0.25 to 3.05 it was possible to read out at least five steps.

Fixing to obtain stable images was accomplished (with 1 Formvar 7/95 S (Shawinigan Chemicals, Inc.), polyvinyl formal of molecular weight of 16,000-20,000, hydroxyl content of 7.0-9.0 (expressed as percent polyvinyl alcohol), acetate content of 9.513.0 (expressed as percent polyvinyl acetate), formal content of 80 (expressed as percent polyvinyl formal and having a specific gravity of 1.229.

B-hydroperfiuoroalkanesulfonic acids are prepared by the addition of sodium bisulfite to perfluoro-olefins in the presence of a. buffer such as borax. See for example, Koshar et 211., J. 'Am. Chem. Soc., 75, 4595 (1053). The salts can he made from the acids by conventional methods of neutralization with a base or by double decomposition.

equally satisfactory results) by washing in water and by dissolving out the unexposed areas with dioxane.

In other experiments, it was determined that the amount of silver salt in the above composition could be reduced to 0.1 g. with satisfactory results but with somewhat lower transmission optical densities.

EXAMPLE II EXAMPLE III Example I was essentially repeated except that p-O rnQ-so and a /50, by weight, mixture of (CF CHF'CF SO C11 and CF CHFCF SO Ag were used in place of CF CHFCF SO Ag Similar results were obtained with the silver salt while the metal salt mixture was particularly useful in giving the high sensitivity associated with the silver salt along with the cross-linking of the polyvinyl formal binder in the exposed areas which was caused by the copper salt. This cross-linking made it possible to fix or stabilize more efiiciently.

EXAMPLE =IV Example I was essentially repeated except that 0.5 g. of pinacol hydrate was added and the heat development was found to be effective at lower temperatures, e.g., to C.

EXAMPLE V A photosensitive solution was prepared as follows:

G. Polymethyl methacrylate -methyl ethyl ketone (20% by wt. solution) 10.0 CF CHFCF SO Ag 0.5 Pinacol hydrate 0.5 Tetraethyl malondialdehyde acetal 0.5 1,4-naphthoquinone 0.1

1A low molecular Weight polymer with an inherent "iscosity of 0.20 for a solution containing 0.25 g. polymer in 50 ml. chloroform at 20 C.

The above solution was coated on a 0.002-inch polyethylene terephthalate film support and allowed to air dry. Exposing the photosensitive layer to actinic radiation as in Example I and subsequent heating of the exposed layer to C. eifected the dry development of a visible image.

A similar solution was prepared in the absence of the polymethyl methacrylate binder using a small quantity of the methyl ethyl ketone solvent. The solution was coated on a porous paper support, exposed and heat developed to give a similar image.

(2.), a boiling point of 325-360 C. (760 111111. Hg) and a pour point of 19 C. (ASTM D-97).

vinyl formal binder of that example was replaced with other polymeric acetals such as various polyvinyl butyral polymers which are commercially available. These included a polyvinyl butyral polymer of molecular weight 45,00055,000, an hydroxyl content of 9.013.0 (expressed as percent polyvinyl alcohol), an acetate content of -2.5 (expressed as percent polyvinyl acetate), a butyral content of 88 (expressed as percent of polyvinyl butyral), and a specific gravity of 1.083 (Shawinigan Chemicals, Inc. Butvar B-76). Results were similar to those obtained in Example I.

EXAMPLE VII A photosensitive mixture was prepared from the following ingredients:

Butyl benzyl phthalate0.4 g.

Phenanthrenequinone0.06 g.

Tri-n-heptylamine (1 mg. per ml. in acetone solution) Acetone1 ml.

Polyvinyl butyral (described in Example VI)1.33 g.

This mixture was applied to 0.00l-inch polyethylene terephthalate film with a doctor blade set at 0.006 inch and dried overnight. The dried coating was exposed refiectographically (through the support) to a contacting resolution chart printed with blank ink on white paper, using a SOD-watt tungsten filament lamp (General Electric reflector photofiood lamp ASA No. PH/RFL2) at a distance of 6 inches for seconds. After exposure, the element was heated for a few seconds on a hot flat iron surface (l70180 C.) which resulted in the development of a black image in the exposed areas. The image was stabilized by thermal transfer of the unexposed areas to a paper receptor sheet. The transferred areas were converted to a black record by either heating the paper or exposing and heating.

EXAMPLE VIII A photosensitive coating composition was prepared from the following ingredients:

Phenanthrenequinone 0.04

CF CHFCF SO Ag 0.10

Polyvinyl formal 1.0

Acetone 11.0

1 Formvar 7/70 (Shawinigan Chemicals, 1116.), a resin with a molecular weight 21,000 (as a weight average), hydroxyl content of 5-7 (expressed as percent polyvinyl alcohol), acetate content of 40-50 (expressed as percent polyvinyl acetate) and having a specific gravity of 1.2.

The composition was coated and dried as in Example VII and exposed reflectographically to a line image using a 32-watt 60-cycle, l-amp, white-light circular fluorescent tube through a translucent sheet for 10 sec. at 4 in. Then the element was passed over a roller having a temperature of ISO-155 C. to cause the latent image to thermally develop to a brown-black image against a light yellow background. The yellow background color was later removed by an over-all exposure for two minutes at 12 inches distance to the photofiood lamp source described in Example VII. The color was due to unreacted phenanthrenequinone.

EXAMPLE IX A photosensitive coating composition was prepared from the following ingredients:

Phenanthrenequinone-0.05 g.

Ag B Cl (prepared as described in assignees copending application Cripps, U.S. Ser. No. 364,006, filed Apr. 30, l964)-0.3 g.

Polyvinyl formal (as used in Example VIII)-1.0 g.

Acetone10.0 ml.

The composition was coated and dried as in Example VII and exposed through a photographic negative for seconds at a distance of one inch using a phosphorcontaining mercury vapor lamp emitting radiation chiefly from 3600 to 4200 angstroms (Aristo Grid Model B57).

The exposed element was thermally developed by contacting for 30 seconds with a flat iron surface at a temperature of 140-145 C., forming a dark brown image. In a similar composition, the single silver salt was replaced by a mixture of only 0.05 g. each of the above Ag B Cl and the CF CHFCF SO Ag of Example I. With a S-second exposure and similar development conditions, there was obtained a black image.

EXAMPLE X The following photosensitive coating mixture was coated and dried as in Example VII:

Phenanthrenequinone-0.04 g. CF CHFCF SO Ag0.09 g.

Polyvinyl formal (as used in Example VIII)1.0 g. Acetone1l.0 ml.

The dried film was given an imagewise exposure through a photographic negative for 10 seconds at a distance of 6 inches with the photofiood lamp of Example VII, overcoated with a thin layer of paraffin wax, and then thermally developed to a brown-black image by passing over a hot roll preheated to 150 C. A control element, without the Wax overcoating, developed a similar dark brown image. When Water was sprinkled on the surface of both the wax-overcoated developed image and the control image and both were subjected to the exposing light source for about 1 minute, a yellow background stain formed in nonimage areas of the control element but not on the wax overcoated element. Since water accelerated the aging process, it was thus shown that the wax overcoating was helpful in providing improved image stability. Similar improvement in stability was obtained when the overcoating was applied before image exposure.

EXAMPLE XI The following photosensitive coating mixture was coated and dried as in Example VII:

l,4-Naphthoquinone0.08 g.

Acetone-5 .0 ml.

Polyvinyl formal (as used in Example VIII)0.7 g.

The resulting coating was placed in contact with a lead intensifying screen and exposed imagewise for one minute through a lead template to the radiation from a Philips X-ray Spectrograph (North American Philips Co.) operating at 50 kv./ ma. A pale visible image was observed after the exposure and was intensified to a dark, brown-black image by thermal development for about seconds, by contacting with a flat iron surface at a temperature of 145 C.

EXAMPLE XII The following photosensitive coating mixture was coated and dried as in Example VII:

Benzoin phenyl thioether-0.2 g. CF CHFCF SO Ag0.1 g.

Polyvinyl formal (as used in Example VIII)1.0 g. Acetone10.0 ml.

The coating was exposed for 2 minutes through a lettertext photographic transparency at a distance of 18 inches from a 45-amp. carbon arm lamp (Nu Arc lamp Model No. FT26M-2). Upon heating the exposed film at C. for about 1 minute a grey image formed in the exposed areas.

See footnote discussing preparation in Example I.

7 EXAMPLE x111 The following photosensitive coating mixture was coated and dried as in Example VII:

This dried film which contained in initiating system comprising a photoreducible dye plus a reducing agent, was given an imagewise exposure through a photographic negative for 15 seconds at a distance of 12 inches with the photoflood lamp of Example VII. It was then thermally developed by contacting for 1 minute with a fiat aluminum surface at a temperature of 120 C. A dark brown image was formed which was subsequently stabilized (fixed) by washing in acetone to remove the dye. The stabilization step was also useful in lowering the background stain without appreciably affecting the image.

Similar results can be obtained by substituting for the Methylene Blue Dye, equivalent amounts of Safranin Blue B/N phenylglycine, proflavine/N phenylglycine and acriflavine/N-phenylglycine. Adequate images can be formed using the radiation source and heating conditions of Example XXIX.

EXAMPLE XIV A photosensitive composition was prepared from the following materials and coated on 0.002-inch polyethylene terphthalate film with a doctor blade set at 0.006 inch.

G. by weight aqueous solution of polyvinyl alcohol 10.0 Potassium phenanthrenequinone-3-sulfonate 0.05 CF CHFCF SO Ag 0.10 Diethyl phosphonoacetaldehyde diethyl acetal 0.30

A low viscosity grade, about 88% hydrolyzed.

The coating, which was dried in the dark for 3 hours, was given an imagewise exposure through a photographic negative for 10 seconds using the lamp described in Example IX. Thermal development at 140 C. for about 5 seconds afforded a light brown image in the exposed areas.

EXAMPLE XV A photosensitive coating was prepared from the following solution and coated as described in Example XIV.

Phenanthrenequinone--0.05 g.

Diethyl phosphonoacetaldehyde diethyl acetal-0.50 g. Polymethyl methacrylate -1.0 g.

Acetone7.0 ml.

An imagewise exposure of 30 seconds through a photographic negative at a distance of one inch to the lamp of Example IX and thermal development for about seconds on a roller heated to 140 C. afforded a grey-brown record in the exposed areas.

EXAMPLE XVI A photosensitive composition was prepared from the following materials and coated as described in Example XIV:

Phenanthrenequinone0.05 g.

Benzoin methyl etherl.10 g. CF CHFCF SO Ag0.10 g.

Polyvinyl formal of Example VIII1.0 g. Acetone-12.0 g.

A high molecular.- woight resin with an inherent viscosity of 1,20 tor a solution containing 0.25 g. polymer in 50 llll. chloroform at C.

The coating was exposed imagewise for 5 seconds at a distance of one inch to the lamp of Example IX and contact heated at C. for 10 seconds. The coating was then placed against a sheet of paper and passed between two contacting rollers, one of which was heated to 140 C. The emerging sheets were quickly separated. A brown ,black record of the exposed areas remained on the polyethylene terephthalate film and the yellow tinted unexposed areas transferred to the paper sheet. The transferred areas were darkened to a brown-black color by either heating the paper or exposing and heating.

EXAMPLE XVII A photosensitive composition was prepared from the following materials and coated as described in Example XIV.

Phenanthrenequinone--0.05 g. CF CHFCF SO Ag0.10 g.

Cellulose acetate -1.0 g.

Diethyl phosphonoacetaldehyde diethyl acetal0.30 g. Acetone-8.0 ml.

A 30-second imagewise exposure at a distance of one inch to the lamp of Example IX and subsequent thermal development at 140 C. for about 10 seconds afforded a brown image in the exposed area. Thermal transfer of unexposed areas was accomplished by placing the image wise exposed surface in contact with a piece of paper and passing a fiat iron pre-heated to C. over the poly ethylene terephthalate support and immediately separating the two sheets. The transferred area was darkened by heating at C. for about 1 minute.

EXAMPLE XVIII A photosensitive composition was prepared from the following materials and coated as described in Example XIV.

Phenanthrenequinone0.06 g. CF CHFCF SO Ag0.l2 g.

Divinyl ether of 1,4-dimethylolcyclohexane-0.60 g. Polymethyl methacrylate described in Example XV1.0 g. Acetone8.0 ml.

The coating was exposed for 5 minutes as described in Example IX and thermally developed by contacting for 10 seconds with a hot roller at a temperature of 135 C. A brown image was formed in the exposed areas.

EXAMPLE XIX The following photosensitive coating mixture was coated and dried as in Example VII:

Phenanthrenequinone0.04 g.

CF COOAg--0.20 g.

Polyvinyl formal (as used in Example VIII)1.0 g. Acetone-11.0 ml.

The dried film was given an imagewise exposure through a photographic negative for 60 seconds at a distance of 6 inches with the photoflood lamp of Example VII, and then thermally developed to produce an (filings image by passing over a hot roll preheated to EXAMPLE XX A photosensitive solution was prepared from the following ingredients:

Polgvinyl formal solution as described in Example I Phenanthrenequinone-O. 13 g.

Dioxane4.0 ml.

The mixture was coated and dried as described in Ex- Cl1a1'acter1'/.od by havlng an acutyl content of 30.1% and an AS'IM viscosity of 45.

ample VII. The coating was exposed in a 35 mm. camera, f-Z lens, for 15 seconds using two photolights, as described in Example I, to uniformly illuminate an 8 /2 x 11 inch white paper printed with black ink. After exposure the element was thermally developed as described in Example I. A black image corresponding to the white areas of the printed paper was formed.

EXAMPLE XXI A photosensitive solution was prepared from Phenanthrenequinone0.06 g.

Cellulose acetate butyrate 1.0 g.

Diethyl-(4 hydroxy 2,3,5,6 tetrachlorophenyl)phosphate0.50 g.

Triethyl phosphate1.0 m1.

Acetone-11 ml.

and coated as described in Example XIV. The coating was exposed through a photographic negative for seconds using the lamp described in Example IX. Thermal development at 140 C. produced an orange-brown image in the exposed areas. A very weak image formed when the halogenated phosphate was left out of the formulation. When both phosphate esters were omitted no imaging occurred.

EXAMPLE XXII A photosensitive solution was prepared from A mixture of polychlorinated biphenyl compounds (as used in Example II) 0.15 CF CHFCF SO Ag 0.20 Divinyl ether of 1,4-dimethylolcyclohexane 1.50 Polyvinyl formal as in Example VIII 3.50

and coated as described in Example VII. A 15-second exposure was made at a distance of 6 inches to a 100-watt quartz-jacketed, water-cooled, high pressure mercury arc lamp cooled by an auxiliary air blower. Upon heating the exposed coating to 140 C., an orange-brown color formed in the exposed areas.

EXAMPLE XXIII A photosensitive coating on 0.001-inch polyethylene terephthalate film was prepared from a solution containing Phenanthrenequinone-0.025 g. CF CHFCF SO AgO.025 g. Polydioxolane O.5O g.

Tetrahydrofuran4.00 cc.

The dry film was exposed through a photographic transparency for one minute at a distance of 12 inches from a SOD-watt reflector type photoflood lamp as described in Example VII. The exposed surface was contacted with a sheet of white paper, briefly heated with a flatiron surface preheated to 75 C. and the two sheets were quickly separated. The exposed areas transferred to the paper receptor forming a grey-brown record, by repeating the thermal transfer process, using fresh sheets of paper, several copies Were made. By exposing the residual unexposed areas and then thermally transferring this material to a new paper support a grey-brown copy of the original photographic transparency was made. Multiple copies were also made by repeating the procedure.

Characterized by a 20.5% by weight acetyl content and a by weight butyryl content and having a viscosity range of 9.013.5 poises as determined by ASTM method D-134354T in the solution described as Formula A, AS'IM method D-87l-54T.

B High molecular weight film forming polymer prepared by polymerizing dioxolane with boron trifiuoride catalyst.

1 0 EXAMPLE XXIV A photosensitive mixture was prepared from a solution of Phenanthrenequinone0.07 g.

Diethyl phosphonoacetaldehyde diethylacetal0.20 g. Polyvinyl formal as in Example VIII-1.0 g.

Lithium bromide0.087 g.

Acetone9.0 ml. by adding Dissolved in acetone2.0 ml.

and stirring for two minutes. The mixture was coated as in Example XIV forming a dry hazy coating containing a fine dispersion of silver bromide. The coating was exposed through a photographic negative for two seconds using the lamp described in Example IX. Thermal development at 165 C. produced a black image in the exposed area. Similar results were obtained by exposing for 10 seconds at a distance of 2 inches from a -watt tungsten lamp and developing at C.

EXAMPLE XXV A photosensitive coating was prepared as in Example XXIV using 0.15 g. sodium iodide in place of the lithium bromide. The hazy dry coating was exposed for one second using the lamp described in Example IX and developed at C. to form a black image. A pale grey image was visible after exposure and before heating. Similar results were obtained by exposing for 5 seconds using the tungsten lamp of Example XXIV and developing at 175 C. A 4-minute exposure to the tungsten lamp produced a strong red image which turned black during thermal development.

EXAMPLE XXVI To a photosensitive solution prepared from Phenanthrenequinone-0.l0 g.

Polyvinyl formal as in Example VIII-1.0 g.

Acetone-l0.0 ml. was added Finely divided silica having particle sizes of 10-20 millimicrons 0.3 g.

A similar solution was prepared from which the silica was omitted. Coatings were prepared as described in EXAMPLE XXVIII A mixture of Phenanthrenequinone 0.1

CF CHFCF SO Ag 0.3 Polyamide (nylon) resin having a Brookfield viscosity of 110 c.p. at 25 C. in 80% aqueous ethanol 1.6

Distilled water 3.2

Absolute alcohol 10.2

was coated on 0.002-inch polyethylene terephthalate film with a 0.006-inch doctor knife. The dried coating was exposed 30 seconds at 12-inch distance to actinic rediation using a Sylvania Sun Gun II, model SG-55, tungsten The colloidal silica was obtained from an aqueous dispersion of 4 g. silica in 100 ml. water having a pH of 7) refractive index of 1.475 (Dow-Corning).

1 l filament lamp type DWY. Heating with a platen at 160 C. for 30 seconds produced a yellow negative image.

EXAMPLE XXIX A mixture of Phenanthrenquinone 0.1

CF CHFCF SO Ag 0.3 Poly(methy1 vinyl ether/maleic anhydride) of spe- .cific viscosity 2.6-3.5 (high molecular weight grade) 1.7

Acetone 13.

was coated on a 0.002-inch polyethylene terephthalate film with a 0.006-inch doctor knife. The dried coating was exposed 30 seconds at a distance of 12 inches from the lamp of Example XXVIII. Heating with a platen at 160 C. for 10 seconds produced a gray-brown negative image with some background stain.

EXAMPLE XXX A mixture of Phenanthrenequinone 0.1 CF CHFCF S O Ag 0.2 Gelatin (low pH blend) 1.4 Distilled water 13.6

was coated on 0.002-inch polyethylene terephthalate film with a 0.006-inch doctor knife. The dried coating was exposed for 30 seconds at a distance of 12 inches from the lamp of Example XXVIII. Heating with a platen at 160 C. for 30 seconds produced a yellow negative image.

EXAMPLE XXXI A mixture of Phenanthrenquinone 0.1

CF CHFCF SO Ag 0.2 Poly(methyl methacrylate, 35 mole percent acrylonitrile, 40 mole percent-acrylated glycidyl acrylate, 25 mole percent) prepared according to the procedure of assignees copending application of Schoenthaler, Ser. No. 451,300 filed April 27, 1965 1.7

Acetone 13.3

was coated on 0.002-inch polyethylene terephthalate film with a 0.006-inch doctor knife. The dried coating was exposed 30 seconds at a 12-inch distance to the lamp of Example XXVIII. Heating with a platen at 160 C. for seconds produced a yellow-gray negative image.

EXAMPLE XXXII A photosensitive coating was prepared from Phenanthrenequinone-0.08 g.

Polyethylene glycol; avg. mol. wt. 400-020 g. Pinacol hydrate0.2 g.

Polymethyl methacrylate of Example XV0.96 g. Acetoneml.

which was coated on 0.002-inch polyethylene terephthalate film using a 0.006 doctor kinfe. After drying, the coating was exposed for 10 seconds using the lamp of Example IX and was heated at 150 C. for a few seconds. Yellow images were formed in the exposed areas.

Similar colored images were obtained upon adding the plasticizer, dibutyl phthalate, to the above composition.

EXAMPLE XXXIII A mixture of Phenanthrenequinone 0.1 CF CHFCF SO Ag 0.2

' G. Poly(vinyl chloride/vinyl acetate) /10 mole percent, inherent viscosity 0.80 (A.S.T.M. procedure) specific gravity 1.36 1.7

Acetone 13.3

was coated on 0.002-inch polyethylene terephthalate film with a doctor knife. The dried coating was exposed for 30 seconds at a distance of 12 inches from the lamp of Example XXVIII. Heating with a platen at 160 C. for 10 seconds produced a red-brown negative image.

EXAMPLE XXXIV A photosensitive solution was prepared from Phenanthrenequinone0.08 g. CF CHFCF SO Ag-0.1 g.

Cetyl vinyl ether0.6 g.

Pinacol hydrate0.2 g.

Polymethyl methacrylate of Example XV0.96 g. Acetone10 ml.

and coated on 0.002-inch polyethylene terephthalate film using a 0.006-inch doctor knife. After drying for a onehalf hour, the coating was exposed through a photographic transparency for 5 seconds using the lamp of Example IX and was heated at 160 C. for a few seconds. A brown image formed in the exposed areas.

EXAMPLE XXXV A photosensitive coating was prepared from Phenanthrenequinone-0.08 g. CF CHFCF SO Ag0.2 g. Water-soluble starch0.8 g. Pinacol hydrate0.2 g. Acetone-10 ml.

EXAMPLE XXXVI A photosensitive coating was prepared from Phenanthrenequinone-0.08 g. CF CHFCF SO Ag0.2 g.

Polyethylene glycol of mol. wt. 400-0.2 g. Sucrose 0ctaacetate0.5 g.

Pinacol hydrate0.2 g.

Polymethyl methacrylate of Example XV0.96 g. Acetone-10 ml.

A lO-second exposure using the radiation source of Example IX and heating at C. produced brownblack images in the exposed areas.

EXAMPLE XXXVII Films were made from solutions containing G. Ketone photoinitiator, where the ketone is benzophenone, p-hydroxybenzophenone, p-aminobenzo phenone, acetophenone or p-hydroxyacetophenone 0.10 Silver fiuorosulfonate CF CHFCF SO Ag 0.20 15% (by Weight) in acetone of the polyvinyl formal of Example VIII 7.5

by coating the solutions onto 0.002-inch polyethylene terephthalate film using a 0.006 inch doctor knife. The dried films were exposed through a photographic negative to actinic radiation using a Nu-Arc carbon are at full intensity or 8 flashes sec. duration each), a Hico xenon 13 photoflash lamp, model K at one-inch or a Blue-ray printer lamp, model 159. Thermal development at 160 C. for seconds produced a black image in the exposed areas. Addition of 0.5 gram pinacol hydrate aided the image formation.

EXAMPLE XXXVIII A photosensitive coating was prepared from Phenanthrenequinone-ODG g.

Pinacol hydrate-0.5 g.

Triethylene glycol diacetate0.4 g.

Acetic acid (glacia1)1 ml.

Polymethyl methacrylate as described in Example XV- Acetone-- ml.

The slightly tacky coating was exposed for 10 seconds using the lamp described in Example IX. A bright green image was produced in the exposed areas of the film formed. By briefly treating the exposed surface with a cotton swab saturated with acetic acid, the yellow images became red or black depending on the duration of the treatment. Similar color changes took place with ethyl acetate, acetone, methylene chloride or ethanolic acetic acid.

EXAMPLE XXXIX A photosensitive coating supported on a thin glass plate was prepared from 1,4-naphthaquinone0.08 g.

Half-ester of succinic anhydride and polyethylene glycol monomethyl ether of molecular weight 75 0-0.3 g.

Polymethyl methacrylate of Example XV-1.0 g.

Acetone-10 ml.

and was exposed for second using Model K HICO- LITE electronic flash having an output of 200 watt seconds. After exposure it was briefly soaked in a 1:1 by volume ethanol-water solution and heated at about 275- 300 C. during which time the methacrylate in the unexposed areas was removed via depolymerization and volatilization and a gray image remained in the exposed areas.

EXAMPIJE XL A photosensitive solution prepared from Phenanthrenequinone-0. 08 g. CF CHFCF S0 Ag--0.1S g. Diethylphosphonoacetaldehyde diethylacetal9 ml.

was poured onto a thin sheet of asbestos paper and allowed to soak in. An imagewise exposure of seconds using the lamp described in Example IX produced a yellow-brown image which darkened when heated briefly at 160 C.

EXAMPLE XLI A photosensitive solution prepared from Phenanthrenequinone0.08 g. CF CHFCF SO Ag-0.15 g. Diethylphosphonoacetaldehyde diethylacetal0.3 g. Cellulose acetate N,N-diethylaminoacetate--1.5 g. Acetone-10 ml.

The coating was prepared in the usual way and after drying for one-half hour the film was exposed for 20 seconds using the lamp described in Example IX. An orange image was formed in the exposed areas which darkened when briefly heated at C. Continued heating at -180 C. caused the orange image area to become yellow and the unexposed areas to turn red.

In its simplest form, the image-forming layer in the elements of this invention need consist only of (a) a silver salt of a strong acid, (b) a photosensitizer, (c) a hydrogen abstractable material, and. (d) a carrier, preferably a film-forming organic polymer binder. Although a hydrogen abstractable material or hydrogen donor compound (c) is an essential component, while an acid-sensitive organic material (e) and water, or a water-yielding material or compound (f) are components present in preferred compositions, the functions of these three components may be supplied by the polymer binder ((1) alone. Therefore, in defining the image-forming layer of the simplest form of the invention, for 100 parts by weight of polymer binder ((1) there may be present in the imageforming layer in an amount from 2 to 200 parts, preferably from 4 to 50, parts by weight, of silver salt (a). The concentration of photosensitizer (b) is related to that of the silver salt so that for each 100 parts of (a) there may be from 10 to 300 parts, preferably from 20 to 100 parts, of the photosensitizer (b).

In the broadest concept of this invention, component (d) may be a carrier which includes polymer binders as well as sheets of porous paper, asbestos fiber, fiber glass, etc. Since the film forming organic polymer binder is optional, its lower limit of concentration can be zero while the upper limit can be about 95% of the total weight of the image-forming layer (exclusive of solvents). A solvent is normally present, but is usually removed during drying. The amount of solvent in the coating composition depends on the desired coating thickness which may vary from thin coatings, e.g., 0.00001 to 0.001 inch for oflice copy elements, to thicker coatings, e.g., 0.003 to 0.25 inch for relief printing plates as disclosed in US. Pat. 2,760,- 863.

Constituent (c) should be 5 times the weight of constituent (b). However, a manifold excess of constituent (c) can be present.

The layer preferably contains water or a water-yielding material (f), although the water source may be the polymer binder, or even air if processing is carried out in an atmosphere of high relative humidity.

A preferred class of photosensitizers for component (b), the photoreducible materials which are activatable by actinic light and thermally inactive at and below C., includes the substituted or unsubstituted polynuclear quinones which are compounds having two intracyclic carbonyl groups attached to intracyclic carbon atoms in a conjugated carbocyclic ring system. Suitable such materials include 9,10 anthraquinone, l-chloroanthraquinone, 2 chloroanthraquinone, 2 methylanthraquinone, 2 ethylanthraquinone, 2 tert-butylanthraquinone, octamethylanthraquinone, 1,4 naphthoquinone, 9,10 phenanthrenequinone, 1,2 benzanthraquinone, 2,3 benzanthraquinone, 2 methyl 1,4 naphthoquinone, 2,3 dichloronaphthoquinone, 1,4 dimethylanthraquinone, 2,3- diphenylanthraquinone, sodium salt of anthraquinone alpha-sulfonic acid, 3 chloro 2 methylanthraquinone, retenequinone, thymoquinone, 7,8,9,10 tetrahydronaphthacenequinone, and 1,2,3,4 tetrahydrobenz(a)anthracene 7,12 dione. Other photosensitizers which are also useful, even though some may be thermally active at temperatures as low as 85 C., are described in Plambeck US. Pat. 2,760,863 and include vicinal ketaldonyl compounds, such as diacetyl, benzil, etc., alphaketaldonyl alcohols, acyloin ethers, e.g., benzo'in methyl and ethyl ethers, etc.; alpha-hydrocarbon substituted aromtaic acyloins, including alpha-methylbenzoin, alpha-allylbenzoin, and alpha-phenylbenzoin; and photoreducible dyes including those described in Example XIII.

In assignees oopending application of Cripps, Ser. No. 364,006, filed Apr. 30, 1964, U.S.P. 3,347,676, Oct. 17,

1967, there are listed a number of silver salts of strong acids which may be used satisfactorily as component (a). These include silver salts of highly fluorinated alkanesulfonic acids, in particular perfluoroalkanesulfonic acids or beta-hydroperfiuoroalkanesulfonic acids and silver salts of decahydrodecaboric acids, i.e., salts of dihydrogen substituted decahydrodecaborates (2-), or of substituted dodecahydrododecaboric acids, i.e., salts of dihydrogen substituted dodecahydrodecaborates (2-).

When the water-yielding compound (f) is present, useful compounds include alkanols of 4-8 carbon atoms, e.g., t-butyl, n-pentyl, t-amyl and n-octyl alcohol; especially dihydroxyalcohols, e.g., pinacols (and their hydrates) containing tertiary alkyl groups, e.g., t-butyl and t-amyl, and benzpinacol.

The polymer binder (d) can be an organic polymer of molecular weight greater than 10,000, capable of forming hard, coherent, thin films and inert, i.e., substantially free from amounts of labile, covalent halogen. Suitable polymers include alkyl esters of polyacrylic and polymethacrylic acid, e.g., polymethyl methacrylate, polyethyl methacrylate and the corresponding acrylates; cellulose carboxylic acid esters and ethers, e.g., cellulose acetate, cellulose propionate, cellulose acetate butyrate, methyl, ethyl and benzyl cellulose; polyvinyl alcohol and its partial esters and acetals. Thermoplastic polymeric binders are preferred so that the element may be useful in the process of thermal image transfer. However, when thermal transfer is not required, it is also possible to use nonthermoplastic polymeric binders, such as polyvinyl alcohol. As shown in one of the examples, a useful element may be made in the complete absence of a binder, particularly if the light-sensitive system is applied to a porous support, such as paper, in which case the support itself may be considered as a binder.

Suitable acid-sensitive organic materials that have binder properties, in addition to the specific materials listed above, include polydioxolanes and any of the polyoxymethylene compounds that are disclosed in U.S. Patent, Alsup et a1. 2,993,025.

A number of other materials may be present in the image-forming system such as coating aids, e.g., polyethylene oxides, viscosity modifiers e.g., dibutyl phthalate, silica or cellulosic fillers, etc.; colorants, e.g., pigments or dyes which transmit effectively in the actinic region of the spectrum, etc.

The present invention offers the advantage of providing an image-forming system which combines simplicity of use and apparatus with quality results. Image quality which is customarily obtained via elaborate processing (Wet processing) is herein obtained by the simple, dry steps of merely exposing and heat developing. The image has very fine grain, high resolution, high contrast and a wide range of density. A simple fixing step is optional although the developed images are reasonably stable as long as they are not subjected to excessive heat. The system ofiers flexibility in that the developed image may be used as first developed, it may be transferred to a separate receptor support by thermal transfer, or it may be given a washout treatment to physically remove all or part of the non-image areas. By thermal transfer it is possible to obtain both positive and negative images. This thermal development system has potentially high photospeed and can produce images with transmission optical densities greater than 4.0 on a fog-free background.

Because the developed image has very fine grain and very high resolution, it is particularly useful in microfilm reproduction. Light sensitivity of the elements of this invention is more than adequate for any type of Copying operation, e.g., printing by contact or enlargement. Even camera speed has been demonstrated with exposures of about five seconds at f4 with proper illumination and the system has potential capabilities of considerably more speed.

The compositions described above can be coated or applied to various kinds of supports, e.g., plates, films, foils, webs and sheets, including the specific supports and using the coating, spreading and calendering procedures described in each of the patents listed above. Similar layers can be made with or without the use of the solvents described above and/or other solvents. Plasticizers can be used which include dibutyl phthalate and tricresyl phosphate. The versatile character of the compositions is a decided advantage of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An image-yielding element comprising a support bearing an image-forming layer comprising (a) a silver salt of a perfiuoroalkanesulfonic acid or a beta-hydroperfluoroalkanesulfonic acid or a decahydrodecaboric acid, said acid having a stable anion and a pKa no greater than 2,

(b) a photosensitizer capable, upon absorption of actinic radiation, of decomposing said silver salt to liberate a strong acid taken from the group consisting of photoreducible quinones, alpha-diketones, benzpinacolone, polychlorinated biphenyl, brornO- naphthalene and photoreducible dyes,

(c) a hydrogen abstractable material or compound which is a hydrogen donor for said photosensitizer during its absorption of actinic radiation selected from the class consisting of an alcohol, an acetal, diethylene glycol and its monomethyl ether or diacetic acid ester, a polyethylene glycol of molecular weight 400-6000 and tetraethyl malondialdehyde acetal, and

(d) a film forming organic polymer binding agent free from substantial amounts of labile covalent halogen;

said layer being characterized in that for every parts of ((1) there are 2 to 200 parts of (a) and for every 100 parts of (a) there are 10 to 300 parts of (b), and constituent (c) is present in an amount 5 times the weight of (b) but can be present in an amount 0 times the weight of (b) when (d) is the hydrogen donor for (b), the parts being by weight.

2. An element according to claim 1, wherein component (b) is a substituted or unsubstituted polynuclear quinone having two intra-cyclic carbonyl groups attached to intra-cyclic carbon atoms in a conjugation ring system.

3. An image-yielding element comprising a support bearing an image-forming layer comprising (a) a silver salt of a perfluoroalkanesulfonic acid or a beta-hydroperfluoroalkanesulfonic acid or a decahydrodecaboric acid, said acid having a stable anion and a pKa no greater than 2,

(b) a photosensitizer capable, upon absorption of actinic radiation, or decomposing said silver salt to liberate a strong acid taken from the group consisting of photoreducible quinones, alpha-diketoues, benzpinacolone, polychlorinated biphenyl, bromonaphthalene and photoreducible dyes,

(c) a hydrogen abstractable material or compound which is a hydrogen donor for said photosensitizer during its absorption of actinic radiation selected from the class consisting of an alcohol, an acetal, diethylene glycol and its monomethyl ether or di acetic acid ester, a polyethylene glycol of molecular Weight 400-6000 and tetraethyl malondialdehyde acetal, and

(d) a film-forming organic polymer binder free from substantial amounts of labile covalent halogen and at least one of the following:

(e) an acid-sensitive aldehyde precursor or polymeric acetal which produces a color change in the presence of a strong acid having a pKa no greater than 2.0, said color change being suflicient to form a visible image, and

(f) is water or a water-yielding compound selected l7 18 from the group consisting of alkanols of 4-8 carbon 7. A process which comprises atoms, pinacols and their hydrates containing terti- (l) exposing, imagewise, to actinic radiation predomiary alkyl groups and benzpinacol, mating in wavelengths in the ultraviolet and visible said layer being characterized in that for every regions of the spectrum an image-yielding element 100 parts of (d) there are 2 to 200 parts of r having an image-forming layer as defined in claim (a) and for every 100 parts of (a) there are 1, and 10 to 300 parts of (b), and constituent (c) ,is (2) uniformly heating the exposed stratum to a tempresent in an amount 5 times the Weight of perature between 60 C. and 200 C. to efiect dry (b), but can be present in an amount 0 times development of an image. the weight of (b) when (d) is the hydrogen 1O 8. A process which comprises donor for (b), the parts being by weight. (1) exposing, imagewise, to actinic radiation predomi- 4. An element according to claim 3, wherein comnating in wavelengths in the ultraviolet and visible ponent (b) is a substituted or unsubstituted polynuclear regions of the spectrum an image-yielding element quinone having two intra-cyclic carbonyl groups attached having an image-forrning layer as defined in claim 3, to intra-cyclic carbon atoms in a conjugation carbocyclic l5 and ring system. (2) uniformly heating the exposed stratum to a tem- 5. An element according to claim 3, wherein component perature between 60 C. and 200 C. to eflect dry (c) is an alkanol of 4-8 carbon atoms. development of an image.

6. An element according to claim 3, wherein component (e) is a polymeric acetal which contains intra- 20 References Cited linear units of the structure UNITED STATES PATENTS 3,218,166 11/1965 Reitter 9667 -CHz-(|3HCH2(|3H- 3,218,168 11/1965 Workman 96-67 25 NORMAN G. TORCHIN, Primary Examiner l M. F. KELLEY, Assistant Examiner US. Cl. X.R.

where R is H or CH CH CH 961 14.1 

